Second Attempt

As mentioned previously, after I’d built my first attempt at the chest block part I realized that the plans I used to do it were incomplete – lacking in a couple features that had already been incorporated into the design plans, and a few of the angles had changed somewhat between that design and the current one. The process of creating the templates I used for the paper chest was fairly labor-intensive, as well: I did it by breaking up the chest design into triangles, calculating edge lengths, and putting triangles on graph paper with those edge lengths. The resulting “unfolded mesh” was adequately precise for its purpose but it had too many flaws to be used for a final part. So this time around I started with my Blender model, and used the “unfolder” script to turn a simplified version of the chest block into a template for building the part from styrene. As before, I used 1mm plastic sheet for the construction, and cut mitred edges where segments were to join.

The process yielded a much better template, and so the parts went together with fewer gaps and better consistency between the two sides. However, after finishing construction of the part I discovered that something in the process was adding length to the dimensions of the chest block: it could be that I didn’t cut the parts out quite right but I think mostly it was a problem with the mitre joins. They weren’t cut quite carefully enough and so they’re not precise: I’ve added about 1mm to the width of each chest half and other dimensions have grown around a half-milimeter. I’ll likely just sand down the excess volume to solve the problem. In the future I’ll probably use thinner plastic for the assembly, and possibly account for this error in my part templates, as well.

After the basic block was done, I created guides to help in the placement of the shoulder joints and cut holes for them. I also cut out the recess in the back where the backpack will sit, though I seem to have cut it wider than it ought to be. The opening in the back will be filled with poly putty later on in order to get a good fit for the backpack.

In the views showing the back and underside of the new chest block, it is the segment marked “G” that wasn’t represented in the previous attempt at building the chest block. Rather, plates F and H simply met at an edge at the bottom of the chest block. Additionally, the “H” plates were parallel to each other in the previous chest block attempt, where now they are angled, so that the areas nearest the middle of the body extend farther back.